322 MANUAL OF EQUINE MEDICINE. 



Other reasons have also been given in support of the view 

 that tetanus is a blood disease. 



The assertion that the spasms begin in muscles which 

 have no anatomical connection with the injured nerves 

 cannot be regarded as of any weight whatever in deciding 

 in favour of the affection being a blood disease. 



In what manner is the blood then altered ? 



Are we to look to changes in its quality, or to the presence 

 in it of some endopathic poison resembling strychnine in 

 its effects, as suggested by Sir T. Watson and Dr. Eichard- 

 son ? Or are we to look for the presence of living microbes 

 in the blood, as^ indeed, have been demonstrated by M. 

 Pasteur in patients suffering from hydrophobia 1 



This question for the present remains unsettled, but it 

 seems not improbable that tetanus may eventually prove to 

 be due to the presence and development of living germs in 

 the blood and tissues. 



We may, perhaps, the more easily understand tetanus as 

 a disease if we first consider cursorily some of the phenomena 

 exhibited by a tetanized muscle. 



If a nerve-muscle preparation be carefully made and preserved, and 

 the nerve be irritated in anyway whatever, the muscle will respond to the 

 application of this new incident force by an aggregate of changes which 

 are collectively spoken of as a contraction. 



Further, if during the period of maximum intensity of the contrac- 

 tion another equal stimulus be applied, the additional response will be 

 nearly equal to the first. 



A lever suitably attached to the muscle will be raised very nearly 

 as much again, the amount of the two contractions will be nearly twice 

 that of the first alone. If more stimuli of equal intensity be succes- 

 sively applied, with each subsequent irritation, the amount of the conse- 

 quent contraction becomes gi-adually less, until at length, when the 

 stimuli reach a certain number in a given time, the lever is not raised 

 higher, but the component contractions are apparently united, fused, 

 as it were, to form a single continuous uniform contraction, and though 

 really still existing, are not to be indicated by ordinary instruments. 



This condition of a muscle, which is called tetanus, may be pro- 

 duced by the interrupted current, or by any rapidly repeated shocks. 

 The frequency of the stimuli needed to produce tetanus differs in dif- 

 ferent cases. 



